location-list: Reload recent locations instead of adding new

Each "Scan folder" adds a new location in the list if it is not already
there. Consequently, the location list may be pretty overfilled. Let's
reload the recent items after each "Scan folder" instead. As the result,
max 5 recent locations will be always shown.

https://bugzilla.gnome.org/show_bug.cgi?id=695421